Doctors treating Richard Hammond said last night that the Top Gear presenter had "suffered a significant brain injury" when the jet-powered dragster he was driving crashed after reaching speeds approaching 300mph.

The father of two had to be cut from the wreckage and was flown by air ambulance to Leeds General infirmary, which issued a statement about his condition after his wife and children had been to see him. In the statement, the hospital trust said: "Mr Hammond has suffered a significant brain injury. It's still giving cause for concern as it is still early after the injury. However, we are reasonably optimistic that he will make a good recovery."

Spinal injuries

The two most serious possibilities are that he has suffered damage as a result of his brain slamming against the inside of his skull during the crash. Because of that, arteries could have been ruptured. Doctors will also be fearful of spinal injuries.

As well as his family, Hammond, 36, was visited by Top Gear co-presenters Jeremy Clarkson and James May. Clarkson reported that Hammond had smiled briefly at him when he quipped: "The reason you're here is because you're a crap driver."

Yesterday the BBC defended its safety guidelines as the police and health and safety experts launched joint inquiries into the crash. The corporation said it had a "rigorous safety regime" for staff who put themselves in potentially dangerous situations, but it revealed it had also launched an internal investigation.

The BBC could face huge fines if it is found that proper guidelines were not followed before Hammond was allowed to drive Vampire at an airstrip near York. Investigators will want to know if he was attempting to break the British land speed record during what was apparently his final run in the vehicle. Witnesses said he was in "euphoric" mood during filming at a former RAF base in Elvington. They said the car appeared to suffer a tyre blowout and veered to the right before it crashed.

One of the braking parachutes was deployed but as Vampire flipped over several times, the nose cone of the car was destroyed and pieces of debris were strewn across the airfield. The dragster came to rest upside down with Hammond still strapped into the cockpit. He was breathing but unconscious when rescuers reached him. Late yesterday afternoon, the car was loaded on to a lorry and taken away for a forensic examination.

"It is very unusual ... and this is one of the reasons why we are working with the police," said Keith King, a principal inspector with the Health and Safety Executive. "Our file will consider what action is appropriate bearing in mind what evidence comes out of the investigation. We need to find out everything we can about what arrangements had been made for this event, how many people were involved and everything else which may be relevant." The executive has asked the film-makers for all footage of the event including preparations and trial runs before the accident.

Organisers said Hammond's only complaint before the crash had been that his seatbelt was too tight. Malcolm Pittwood, a spokesman for the organisers, Primetime Land Speed Engineering, said Hammond had been taking the dragster "up through the speeds, getting faster and faster each time" before the accident.

Speed record

The company's owner, Colin Fallows, who set the British land speed record of 300mph in July, and his business partner, Mark Newby, issued their own statement: "The vehicle which Richard Hammond was driving all day yesterday had been prepared and was being operated to the highest of standards. Standards which we have maintained for many years in the safe operation of such vehicles.

"We are cooperating and will continue to cooperate fully with the necessary authorities in every way possible. But at this moment our thoughts are with Richard Hammond and his family and [we] are praying for his swiftest recovery."

RAF fighter pilot Andy Green, holder of the world land speed record of 763mph, said Hammond had been "very brave" to drive the vehicle. "It's a very brave thing of Richard to do to step into a very skilled, very specialist sport pretty much from cold. He would obviously have had some practice but he hasn't lived with this, he hasn't developed the car, he hasn't been part of it for a long time," he told BBC Radio Five Live.

Hammond has taken the long route to stardom, via BBC Radio York and stints in PR for Renault and Ferrari before getting a presenting job on the satellite channel Men & Motors in 1998. But since joining Top Gear in 2002 he has hosted the popular children's science show Brainiac on Sky One, an ITV teatime talkshow, and BBC1's Should I Worry About?

Coming weeks after the death of the Australian wildlife guru Steve Irwin, the accident is bound to focus attention on the lengths to which presenters will go to ensure they hold viewers' attention. The former Top Gear presenter, Steve Berry, noted how TV had changed over the years. In the past it would have been sufficient to film the car and interview the driver. "That's not any good any more ... the audience and the TV producers want you as a presenter to be there, on the inside."